Nov 2, 2005.
Meeting minutes.
7:03 PM and Bill introduced Chat Hull senior at the UVa Physics Dept.
He used Spitzer data in a project at
"The Youngest Stars:
Studying the earliest stages
of star formation
with data gathered
by the Spitzer Space Telescope."
The IRS (Infra Red Spectrograph) images accretion disks in star forming
regions. Chat showed us a cool animation of this by Robert Hurt.
The Spitzer was launched in 2003 and is the 4th of the Great
Observatories, covering the infrared. The protostars are born in clouds
of dust & gas, and the IR light penetrates this very well. In fact
the
only way to see these young stars is in the IR part of the spectrum.
His data was reduced to a number of spectral graphs of class 0 objects.
Then he showed us a cataclysmic variable, AE Aquarii, where a white
dwarf was not accreting the large star's material but is slinging it
off.
Then he showed us a spectrum where a star had hollowed out its disk,
possibly by a "hot
a torus.
Stellar formation features:
- Accretion
- Outflow jets
- Shocks
In the beginning stages of stellar formation, we start with a cloud of
gas.
- Class 0 has the beginnings with the cloud slowly collapsing.
- Class 1 there are some features to detect, outflows start to form
- Class 3 and the envelope is gone and the disk starts to coagulate.
- Class 4 is a star, formation is complete.
How long does the class 0 phase last? That's a major research question.
There are few known, they are quite rare. There weren't any scopes
before Spitzer that could detect them, so of course little is known.
Stellar shocks:
- Disk to star
- Outflow shocks
- Envelope to disk shocks.
This last was theoretical and was an important discovery. Bipolar
outflow jets dissipate angular momentum, ejected matter has a low
density, and are sources of certain lines which are observed in
protostellar spectra.
Then Chat talked to us about the iron lines & outflows of L1641 where
outflow jets were found which agreed with theory quite well.
NGC 1333 Detection of Disk Accretion Shock? Where a number of H2O lines
were detected where the envelope matter was accreting onto the
protostellar disk (the third of the above mentioned stellar shocks).
Conclusions:
- Class 0s are rare & not well understood
- Progress - We successfully distinguished between outflow and disk
accretion shocks
- H2O lines in NGC 1333 may be a disk accretion shock.
- I calculated upper limits of H20 line fluxes in class 0 sample, some
agreed with theory, giving us upper limits on accretion rate.
- The future: we'll search for more disk shocks, do more thorough
comparison with the theoretical models and further enhance our
understanding of the beginnings of our Universe and the evolution of
its youngest stars.
Thank You.
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At 8 PM Bill took the floor and announced that it was time for the
elections.
These are the nominees:
Secretary (acting), Wes Epperly
Treasurer, Larry Saunders
Vice President, Richard Drumm
President, Steve Layman
There were no other nominations and the election proceeded with a
raising of hands and all were elected unaminously.
Bill announced that Phil Ianna, our dark sky advocate will be our
speaker for December's meeting.
The club Xmas party is Dec 10th at Bill's house, 6PM.
We had a few issues which arose, what could we be doing better next
year and Bill thought that the CAS Council meeting (when there is one
next) would be a fine time to get into this. Bill then told us he is
relieved to not have the president's duties but was thrilled to have
been our president. He adjourned the meeting at 8:08PM and a Mars
observing session with the 26" was enjoyed.